NEW YORK, NEW YORK - SEPTEMBER 07: Karen Khachanov serves against Learner Tien of the United States during their Men's Singles Fourth Round match on Day Nine of the 2026 US Open at USTA Billie Jean King National Tennis Center on September 07, 2026 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Matthew Stockman/Getty Images)

NEW YORK, NEW YORK - SEPTEMBER 07: Karen Khachanov reacts against Learner Tien of the United States during their Men's Singles Fourth Round match on Day Nine of the 2026 US Open at USTA Billie Jean King National Tennis Center on September 07, 2026 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Matthew Stockman/Getty Images)

NEW YORK, NEW YORK - SEPTEMBER 07: Karen Khachanov reacts against Learner Tien of the United States during their Men's Singles Fourth Round match on Day Nine of the 2026 US Open at USTA Billie Jean King National Tennis Center on September 07, 2026 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Matthew Stockman/Getty Images)

NEW YORK, NEW YORK - SEPTEMBER 07: Karen Khachanov reacts against Learner Tien of the United States during their Men's Singles Fourth Round match on Day Nine of the 2026 US Open at USTA Billie Jean King National Tennis Center on September 07, 2026 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Matthew Stockman/Getty Images)

NEW YORK, NEW YORK - SEPTEMBER 07: Karen Khachanov reacts against Learner Tien of the United States during their Men's Singles Fourth Round match on Day Nine of the 2026 US Open at USTA Billie Jean King National Tennis Center on September 07, 2026 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Matthew Stockman/Getty Images)

NEW YORK, NEW YORK - SEPTEMBER 07: Learner Tien of the United States looks on against Karen Khachanov during their Men's Singles Fourth Round match on Day Nine of the 2026 US Open at USTA Billie Jean King National Tennis Center on September 07, 2026 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Matthew Stockman/Getty Images)

NEW YORK, NEW YORK - SEPTEMBER 07: Learner Tien of the United States returns a shot against Karen Khachanov during their Men's Singles Fourth Round match on Day Nine of the 2026 US Open at USTA Billie Jean King National Tennis Center on September 07, 2026 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Matthew Stockman/Getty Images)

NEW YORK, NEW YORK - SEPTEMBER 07: Learner Tien of the United States serves against Karen Khachanov during their Men's Singles Fourth Round match on Day Nine of the 2026 US Open at USTA Billie Jean King National Tennis Center on September 07, 2026 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Matthew Stockman/Getty Images)